A “time-of-flight” camera is a depth-sensing or range-sensing system that operates by illuminating a scene using a light source (e.g., a modulated source of light at any wavelength or frequency, such as infrared) and capturing light that is reflected from various points of the scene following the illumination. Time-of-flight cameras are typically equipped with an illuminator for illuminating a scene, and a sensor for capturing reflected light from the scene. The reflected light that is captured by a time-of-flight camera sensor may be interpreted to generate a depth profile of portions of the scene within a field of view of the time-of-flight camera. Some time-of-flight cameras may capture and interpret reflected light, and generate depth images or profiles of portions of scenes from such reflected light, dozens of times per second. Depth images or profiles generated by time-of-flight cameras can be very accurate.
Occasionally, where two or more time-of-flight cameras are mounted at scenes with overlapping fields of view, care must be taken when operating the time-of-flight cameras. Where an illuminator of a first time-of-flight camera illuminates a scene, and a sensor of a second time-of-flight camera having an overlapping field of view is exposed, reflections of the light projected onto the scene from the illuminator of the first time-of-flight camera may be detected by the sensor of the second time-of-flight camera, thereby causing the first time-of-flight camera to interfere with depth imaging data captured using the second time-of-flight camera, and resulting in a false construction of a depth profile by the second time-of-flight camera. To alleviate this effect, a discrete modulation frequency may be assigned to each of the time-of-flight cameras that are mounted at a scene with overlapping fields of view, and the times at which such cameras operate illuminators to illuminate scenes and expose sensors to capture reflected light from such scenes may be sequenced (or staggered). In this regard, time-of-flight cameras may operate in concert, while ensuring that a sensor of one time-of-flight camera is exposed only at times when an illuminator of that time-of-flight camera has illuminated a scene, and not at other times, e.g., when an illuminator of another time-of-flight camera has illuminated the scene.
Occasionally, and from time to time, assigning time slots and modulation frequencies to multiple time-of-flight cameras provided at a scene does not eliminate the risk of interference between two or more of the time-of-flight cameras that have overlapping fields of view. For example, where a time-of-flight camera is newly installed at a scene where one or more time-of-flight cameras is already present, or where a time slot or frequency of operation is assigned to a time-of-flight camera and unintentionally coincides with another time slot or frequency of operation assigned to another time-of-flight camera, undesirable interference may be observed within depth imaging data captured using one or both of the time-of-flight cameras. Detecting interference within depth imaging data captured by a time-of-flight camera, or identifying another time-of-flight camera that is causing the interference, are typically difficult tasks.